The Hidden Aspects of A Century of Substance Use Policymaking in Iran

The use of substances, especially opiates, has been a longstanding and significant problem in Iran. In response, Iran has experimented with a wide range of policies including nonintervention, regulation, legalization, prohibition, and criminalization. Exploring Iran’s substance use policies suggests that the Iranian government has been more concerned with byproducts of policies such as financial revenue, promoting diplomacy, and maintaining power, rather than genuinely alleviating the substance trade and addiction. First, we explore how opium taxation was the core substance use policy before oil became the main source of government income. Second, we discuss how conflicts of power between the health sector and other stakeholders relegated the role of the health sector and medical professionals. Lastly, we analyze the post-1979 revolution policies when Iran experienced social desolations, such as during the Iraq-Iran war and the subsequent economic recessions. We reveal that stigmatization and scapegoating of people who use substances have been used as a cover-up to obscure deeper social problems. This historical analysis ultimately reveals that Iran’s substance use policies have largely neglected medical approaches in favor of more oppressive, but politically expedient options

Suboptimal variable structure control of uncertain nonlinear slowly varying systems

In this paper, a new robust suboptimal controller is designed to stabilize a class of uncertain nonlinear time-varying systems with slowly varying parameters. In the design procedure of the proposed controller, first a suboptimal control law is designed for the nominal system based on considering a given cost function and an appropriate Slowly Varying Control Lyapunov Function (SVCLF). After that, a robustifying term is added to the nominal controller in order to vanish the effects of model uncertainties and/or external disturbances in a finite time. For this purpose, a special sliding surface, which is a combination of terminal and integral sliding surfaces, is used. This surface has the advantages of both of terminal and integral surfaces. Due to the structure of this surface, the actual trajectories track the desired one in the finite time. The other innovation of the proposed approach is accessing a chattering-free Controller. Finally, in order to confirm the applicability of the proposed controller and verify the theoretical results, it is applied on a practical benchmark system (a time-varying inertia pendulum). Computer simulations show the efficiency of the proposed controller

Passivity-based optimal control of discrete-time nonlinear systems

In this paper, a passivity-based optimal controlmethod for a broad class of nonlinear discrete-time systems is proposed. The resulting control law is a static output feedback law which is practically preferred with respect to the state feedback law and is simple to implement. The control law has a general structure with adjustable parameters which are tuned, using an optimization method (genetic algorithm), to minimize an arbitrary cost function. By choosing this cost function it is possible to shape the transient response of the closed-loop system, as it is desirable. An illustrative ex ample shows the effectiveness of the proposed approach

Extending Lyapunov redesign method for robust stabilization of non-affine quadratic polynomial systems

The Lyapunov redesign method is basically used for robust stabilization of nonlinear systems with an affine structure. In this paper, for the first time, by suggestion of a simple but effective idea, this approach is developed for robust stabilization of non-affine quadratic polynomial systems in the presence of uncertainties and external disturbances. In the proposed method, according to the upper bound of an uncertain term, a quadratic polynomial is constructed and with respect to the position of the roots of this polynomial, the additional feedback law is designed for robustness of the quadratic polynomial system. The proposed technique is also used for robust stabilizing of a magnetic ball levitation system. When the coil current is the control input of the magnetic ball levitation system, equations of this system are increasingly nonlinear with respect to control input and have quadratic polynomial structure. The effectiveness of the proposed control law is also demonstrated through computer simulations

Robust soft variable structure control of perturbed singular systems with constrained input

This paper investigates the robust soft variable structure (RSVS) control technique for perturbed singular systems with constrained input control. The aim of the RSVS control law, in addition to achieving desirable control performance for the constrained input, is the robust stability of the closed-loop system in the presence of perturbation. In this paper, the RSVS control for perturbed singular systems is designed for two cases. First, it is assumed that the perturbation term vanishes at the origin. In this case, the proposed RSVS controller leads to asymptotic stabilization of the perturbed singular system. In the second case, the perturbed singular systems with non-vanishing perturbation are considered and the robustness of RSVS is also investigated. In this situation, the proposed controller guarantees practical stability of the perturbed singular system. Finally, computer simulations are provided for two examples to verify the theoretical results